I have a replacement alternator on my 6.0 from O'Reillys and I have noticed on my Livewire that on startup my voltage is 11.5 and after a few seconds it goes up slowly to 13.0-13.4 volts. The highest I've ever seen it go was 13.5 but that has only happened a few times. I was reading somewhere that it should be putting out atleast 13.8 volts, preferably 14-14.4 volts. I need to know if I have a weak alternator and what the voltage output is suppose to be?

When you first start your trk it should take about 30sec for the alt to kick in.. After that it should shoot up to 13.8 or higher.. 13.5 max dont seem high enough but im not sure what the OK range is.. Mine will shoot up to 14.4 then settle around 13.9-14.2 and stay in that range.

Just keep monitoring it, If you notice your getting a max of 13.5 now just keep checking to make sure you keep hitting that mark. If it starts to drop you know you have a problem. I bet you are in the normal range tho but on the low side.

More info please how long does your truck sit before you read 11.5 volts. Might be a battery problem but my truck reads 14.2 volts continuously.

Every time I start the truck it shows 11.5-11.6. Even when I start it to Go to lunch from work and I had just drove it to work that morning. I replaced both battery's with Motorcraft factory replacements back in Dec. I was thinking 14-14.4 should be where it rides. I reckon there's always a chance one of them new battery's is weak.

I bet the batts are fine, If anything your alt isnt working right. My last alt would do the same thing yours is doing. After awhile my batt light on the dash would come on every now and then.. It turned out my alt wasnt working right even tho it was tested to be ok.. I put in a new alt and everything works great now. So if I was you I wouldnt worry about it till it gets worse or your batt light comes on.

Dirty Stroke, yesterday I hooked up a DMM to one of the batteries and found out that my Livewire was about .4-.5 lower than what the meter was reading. The other thing is the charging voltage changes with the temperature. On cool mornings I read 14-14.1 and warm afternoons usually 13.4-13.6.

Thanks Qholic! I noticed my voltage is higher in the morning time too. There's a local alternator/starter shop that said they can build me a 140amp alternator for $85! I think I'm going to give that a try and see how that compares

on start up mine is often 11.5 ish then glow plugs kick off and it goes to 12.5 and after another minute its up to 13.6-14 i normally put her in drive soon as the glow plugs kick off and soon as a hit the gas it pretty much instantly climbs to 13.6-14.1

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